Method Statement for Dry Gunite Shotcrete Works.

Scope of Work.

The purpose of this method statement is to outline the materials and labor required to undertake the Dry Gunite Shotcrete Works.

Equipment to be used for Mobilization.

• High Pressure Air Compressor
•  Blastcrete Gunite machine 
• Steel and wooded trowel  
• Small hand tools 
• Aluminum straight Edge  
• PPE 

Materials to be used.

Shotcrete STS1010.

Mobilization Procedure.

General.

Prior to works commencing, the Project / Site Engineer shall ensure that the areas allocated to subcontractor are provided by the client. 

Subcontractors assist and advise their staff and Sub-contractors (Pre-qualification to be reviewed entering from the designated gate accordingly. 

Subcontractor to comply with all legal requirements.

Only authorized vehicles will be allowed to enter at site and coordinate with HSE Department. 

Working Platforms: 

Scaffolding: 

The following requirement to be followed during the erection of scaffolding to withstand the force or 

load and maintain proper safety accessibility: 

The height of the erected scaffolding as per the site condition is 8 meters. 

Scaffolding to be designed to withstand the force of load of Technicians along with load of Nozzle 

system. 

Scaffolding erection and dismantling will be carried out by a competent scaffolding erector and 

scaffolding inspector at site. 

The access ladder will be placed at an angle of 4:1 and will be extended 1 meter above the platform for safe holding and landing on the platform. 

The distance between the toe board and top rail shall be not more than 113 cm as per standard. 

If four platform boards are used the width shall not be less than 80cm when two persons or materials are used. 

The width of the platform shall not be less than 60cm if 3 platform boards are used. 

The height of the toe board shall not be more than 15 cm. 

Proper tagging of the scaffolding shall be followed during erection, dismantling and while people are working on the scaffolding. 

Suitable scaffolding components as per the requirement to be used for erecting the scaffolding. 

Proper Lockup and set up of tubular columns as well as platforms. 

The minimum distance requirement in between the finish level of the wall and platform should be 300 mm to facilitate masonry work. 

The distance between each platform should be max 2-meter Height. 

Extra tubular columns, toe guard, mid rails, should be provided all around the platform. 

The Sequence of Events:

Scope of Works: Cleaning and Reinforcement fixing:

Clean the surface using hydro blasting to make the surface free from dust, loose mud and unwanted loose materials, etc.

Spray & Fill up Shotcrete STS1010 gunite mix.

Spray apply wet gunite ready-mix second/multiple coats on the wall surface to achieve desired thickness & towel rough finish with minor undulations as per the actual wall profile.

Operating requirement.

As Guniting is a sprayed concrete application it requires higher-pressure air during the application. 

Suitable compressor for the application to be used. 

Prior to carrying out the below gunite procedure main contractor to ensure the installation of the scaffolding for the work location after evaluating the height and area of workplace. 

Site setting out survey to be carried out by the main contractor to verify the vertical and horizontal alignment of the shoring piles surface are within the required thickness of the guniting. 

Surface Preparation.

Clean to make the surface free from dust, mud and unwanted loose materials, etc. using water jetting with 200- 250 bar pressure.

Hard soil or any concrete settings on the wall surface shall be chipped off by using suitable methods.

Site Set up: 

The site will be organized to offer the most efficient application of the sprayed concrete. Due 

Consideration will be given to the requirements to always maintain a safe method of work. 

The pump will be in the most appropriate position based on a maximum pumping horizontal length of 50 meters and vertical pumping height of 30 meters. 

Compressor shall be located near the application area to provide sufficient air supply for the application. 

Tools and blow out heads will be kept with the pump. 

Fresh water shall be made available as per site requirements. 

Gunite work.  

As per the site condition, the application shall be done as following: 

Set out guide level or thickness markers from the surface for required thickness.

Fix thickness markers / guide points on the surface to a frequency as required by site condition. (at least 2m x 2m square pitch)

Spray & Fill up wet gunite mix on the surface as a rough coat.

The wet gunite will be applied in multiple layers from the surface; the first layer thickness shall not

exceed 40-50 mm. (no. of layers increases with thickness)

Minimum cover shall be maintained from the mesh surface to the outer layer of the wet Gunite

depending on the actual surface condition at site.

The wet gunite shall be applied either working from the top to bottom or vice versa as per the site

condition for the rush coat and shall be applied working from top to bottom for the finish coat.

The surface of wet guniting shall be trowel finished.

Shotcrete shall not be applied in high winds, when raining or ambient air temperature exceeds 45 deg. 

 Do not reuse rebound material. Dispose of surplus material off site.

Curing.

Curing will be 3 times/day for 72 hours by using Water and plastic sheet to keep the area wet as per  project specification.